Cast: Use DSCP AF41 for all traffic if possible.

Turns on DSCP AF41 to give cast traffic a higher priority.

BUG=385768
TBR=miu

Review URL: https://codereview.chromium.org/344953003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278683 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 28 insertions, 0 deletions

diff --git a/media/cast/transport/cast_transport_sender_impl.cc b/media/cast/transport/cast_transport_sender_impl.cc
index 2f51a93..c440c6c 100644
--- a/media/cast/transport/cast_transport_sender_impl.cc
+++ b/media/cast/transport/cast_transport_sender_impl.cc
@@ -7,6 +7,7 @@
 #include "base/single_thread_task_runner.h"
 #include "media/cast/transport/cast_transport_config.h"
 #include "media/cast/transport/cast_transport_defines.h"
+#include "net/base/net_util.h"
 
 namespace media {
 namespace cast {
@@ -66,6 +67,11 @@ CastTransportSenderImpl::CastTransportSenderImpl(
                             this,
                             &CastTransportSenderImpl::SendRawEvents);
   }
+  if (transport_) {
+    // The default DSCP value for cast is AF41. Which gives it a higher
+    // priority over other traffic.
+    transport_->SetDscp(net::DSCP_AF41);
+  }
 }
 
 CastTransportSenderImpl::~CastTransportSenderImpl() {
diff --git a/media/cast/transport/transport/udp_transport.cc b/media/cast/transport/transport/udp_transport.cc
index bcce4f7..9669b17 100644
--- a/media/cast/transport/transport/udp_transport.cc
+++ b/media/cast/transport/transport/udp_transport.cc
@@ -54,6 +54,7 @@ UdpTransport::UdpTransport(
       send_pending_(false),
       receive_pending_(false),
       client_connected_(false),
+      next_dscp_value_(net::DSCP_NO_CHANGE),
       status_callback_(status_callback),
       weak_factory_(this) {
   DCHECK(!IsEmpty(local_end_point) || !IsEmpty(remote_end_point));
@@ -88,6 +89,11 @@ void UdpTransport::StartReceiving(
   ScheduleReceiveNextPacket();
 }
 
+void UdpTransport::SetDscp(net::DiffServCodePoint dscp) {
+  DCHECK(io_thread_proxy_->RunsTasksOnCurrentThread());
+  next_dscp_value_ = dscp;
+}
+
 void UdpTransport::ScheduleReceiveNextPacket() {
   DCHECK(io_thread_proxy_->RunsTasksOnCurrentThread());
   if (!packet_receiver_.is_null() && !receive_pending_) {
@@ -162,6 +168,16 @@ bool UdpTransport::SendPacket(PacketRef packet, const base::Closure& cb) {
     return true;
   }
 
+  if (next_dscp_value_ != net::DSCP_NO_CHANGE) {
+    int result = udp_socket_->SetDiffServCodePoint(next_dscp_value_);
+    if (result != net::OK) {
+      LOG(ERROR) << "Unable to set DSCP: " << next_dscp_value_
+                 << " to socket; Error: " << result;
+    }
+    // Don't change DSCP in next send.
+    next_dscp_value_ = net::DSCP_NO_CHANGE;
+  }
+
   scoped_refptr<net::IOBuffer> buf =
       new net::WrappedIOBuffer(reinterpret_cast<char*>(&packet->data.front()));
 
diff --git a/media/cast/transport/transport/udp_transport.h b/media/cast/transport/transport/udp_transport.h
index 17b0d77..1a56850 100644
--- a/media/cast/transport/transport/udp_transport.h
+++ b/media/cast/transport/transport/udp_transport.h
@@ -12,6 +12,7 @@
 #include "media/cast/transport/cast_transport_config.h"
 #include "media/cast/transport/cast_transport_sender.h"
 #include "net/base/ip_endpoint.h"
+#include "net/base/net_util.h"
 #include "net/udp/udp_socket.h"
 
 namespace net {
@@ -46,6 +47,10 @@ class UdpTransport : public PacketSender {
   // Start receiving packets. Packets are submitted to |packet_receiver|.
   void StartReceiving(const PacketReceiverCallback& packet_receiver);
 
+  // Set a new DSCP value to the socket. The value will be set right before
+  // the next send.
+  void SetDscp(net::DiffServCodePoint dscp);
+
   // PacketSender implementations.
   virtual bool SendPacket(PacketRef packet,
                           const base::Closure& cb) OVERRIDE;
@@ -72,6 +77,7 @@ class UdpTransport : public PacketSender {
   bool send_pending_;
   bool receive_pending_;
   bool client_connected_;
+  net::DiffServCodePoint next_dscp_value_;
   scoped_ptr<Packet> next_packet_;
   scoped_refptr<net::WrappedIOBuffer> recv_buf_;
   net::IPEndPoint recv_addr_;